Cam recommendation for Mopar

[Scott Wasko]

572" Mopar (4.50 X 4.50), 14:1 compression, B1BS heads with 2.25/1.88 valves (peak flow is said to be 365 intake, 245 exh), 7.100 rod, single 4 barrel Indy Intake, 1250 alky carb. Motor is run with a glide in a 1800 rear engine dragster. Looking for cam with optimal performance as motor has never run to potential. Cam that has been run in motor is way too small (272/280, 110) and, to me, motor combo is not the best with bigger cubes and small heads (B1BS is basically a stock replacement head and has some port work done by Koffels).

Looking forward to your recommendation.

[buschracing]

i am sure you know this, but that 2.25 valve is more suited to a 450" big block turning 8000 rpm. your 572 needs a LOT more head on it, not more cam. You are all out of head at about 6000 rpm. i would think a raised runner head using a 2.4-2.5" intake and 1.88 ex valve would be a about right. I am ignorant of the Mopar stuff. Do they make a head like this with a matched single 4 intake??? Maybe some old Mopar Pro Stock heads from the late 80s or early 90s would work well...

Once you have the induction more in line, i am sure Jay would design you something. With your current heads, i figure he wouldnt touch it...

Camming your deal now would require something crazy like 290@.050 with 108 lobe sep. The overlap would be thru the roof. P/V clearance non-existent. all in all a bad deal...

[Chris Uratchko]

There is a set of B1MC heads forsale that used to be on Bruce Lagorys engine in NMCA Real Street. It's on Racingjunk.. Heads and intake done by BES. The car ran in the 8's with that stuff at 3500 pounds, 515 inchs.

2500 bucks.... can't beat that!!

[STEFF]

Yikes!!! B1BS heads don't belong on a 572. Who talked ya' into that? You should have a set of these on that 572.

http://www.nrcperformance.com/images/predator/diag_overall01.jpg

www.nrcperformance.com/

[Scott Wasko]

I'm a Chevy guy and don't know much about Mopar stuff but I can tell it is way under headed for the size of the motor. It a buddy's motor and it is what it is--he'd love to have new heads, etc but the funds aren't there so he's trying to work with what he has. At this point, we're trying to optimize what he has.

Funny someone brought up P to V clearance....we measured this motor and came up with over .400 thou of clearance. Double and triple checked it. I feel like we're missing something--doesn't this sound right? Heads are 65cc and pistons have approx .100 dish. Checked at 10 before and after TDC using a degree wheel.

[Jay Allen]

Let's look at some stuff here.

2.25/1.88 valves
peak flow is said to be 365 intake
motor has never run to potential
Cam that is way too small
272/280, 110

The camshaft is NOT your problem unless it is like 680 lift and 180 at .200!

A little trick I learned a while back was to look at the sq area of a valve. Let's do that. Area of a circle is (pi X R^2]. Thus.......

3.14 X (1.125)^2 = 3.974. Now, what does this mean? A *Very good port* will move 110% of this value. A *Good Port* will move 100% of this area. Below that?
110% X 3.974 = 437 cfm
100% X 3.974 = 397 cfm
95% X 3.974 = 377 cfm
90% X 3.974 = 358 cfm

365/397 = 91.9%.

Now the following is S.W.A.G.

Let's say the port is as long as a BBC. 6". If this were a BBC with STD port placement, valve placement, the port would be (+/-) about 325cc. Now calculate average cross section.

325cc/16.39 = 19.83 CID. 19.83/6 = 3.305 average square inches.

Interesting.

365 cfm / 3.305 sq in = 110.44 CFM/sq in.

There's your problem. The LAST thing you need right now is a camshaft. If & when you get the heads fixed, THEN you'll need a camshaft. But right now:

-You are volume limited in the head.
-This is compounded by the alcohol.
-The amount of air through that intake port is low, very low.

Not what you wanted to hear, but its the truth.

[Scott Wasko]

I checked the intake lift and it was .440 when measured at the pushrod....with 1.58 rockers about .695 lift. I know the heads are killing this thing...we've known it since his old man thought it would be a great idea to build a big cube motor but he wouldn't listen or understand that he would have been better off with a 498 with the heads he has.

I thought there is or could be a way to use the camshaft to "trick the motor". I gotta believe the small cam now isn't helping anything either. Obviously this motor will never run like it's a 572 but trying to find way to improve it and pick it up a little.

[Jay Allen]

Most of the time guys are worried about making a part too big. I have to say, if the rest of the junk is matched, that is damn hard to do. Especially on a race engine. What kills them worse is when parts are too small. You have decent 440cid heads IMHO. And guess what? The engine performs like that. The cam is going to have to be so big that cranking compression and dynamic compression will suffer. It'll make some huge dyno number but the engine will never accelerate down the track. A smaller cam (duration wise) almost always outruns a larger (duration) cam. And if the engine doesn't want to rev up, the increase the head cross section and flow. It'll rev up then and accelerate at the same time. If you keep buying cams you are throwing money away. I cannot with a clear conscience recommend something. Well, I can, but it ain't cam related.

Good Luck.